Method of separating glycerides



July 1l, 1950 v. J. MUCKERHEIDE METHOD 0F SEPARATING GLYCERIDES Filed Aug. 30, 1945 "QAM llllm L NVENTOR. 40M

lllll `Illll IIIIIII IIIII Patented July 1950 METHOD F SEPARATING GLYCEBIDES victor J. Muckerheide, cincinnati, om, minor to Emery Industries, Inc., Cincinnati, Ohio, a

corporation of Ohio Application August 30, 1945, Serial No. 613,660

Claims.

This invention relates to a method of treating ,the mixtures of triglycerides occurring in natural animal, vegetable and marine oils to separate the glycerides containing the greater proportion of solid high melting saturated fatty acids from those containing a greater proportion ofliquid low melting unsaturated fatty acids.

The process of this invention is generally applicable to the mixed triglycerides occurring in animal fats such as hog fat and tallow, the vegetable oils such as soya bean oil and cottonseed oil and fish oils such as sardine or herring oil. This application is a continuation in part of my copending application Serial No. 546,416, tiled July 24, 1944 now abandoned.

Though the present invention is applicable to the fractionation of mixed triglycerides generally, it is disclosed primarily in relation to the manufacture of lard oil which may be considered both a typical product chemically and a standard commodity commercially which has long been of great importance in numerous industrial fields, particularly metal working and textile weaving and finishing.

Lard oil is the more liquid portion of hog fat and may be produced from lard but is ordinarily produced from the inedible grade of hog fat known as white grease or yellow grease. Lard oil commands a premium price over the white grease from which it is produced, its enhanced value being due to the fact that it is a liquid and remains liquid at temperatures which would nrmally be encountered in shipment or in use.

For many years lard oil has been produced by a relatively standard process in which the white grease is iirst slowly and carefully chilled for a period of from three to six days to a temperature of approximately 50 F. The chilled white grease is then placed in bags and pressed slowly in order to express the lard oil. 'I'he slow chilling is necessary in order to obtain a crystal which will permit release of the lard oil in the pressing operation.

'Ihe quality of the lard oil produced by this method, as measured by the cold test which is the temperature in degrees F. at which the oil will lust ilow, is controlled by the temperature at which the pressing is carried out and the care' exercised in chilling.

B'y this method fromv50 to 65% by weight of lard oil of 40 pour point may be obtained. The solid glycerides which constitute the remainder are known as stearine. Although having a higher melting point than the original white grease it ordinarily commands no premium price. The

(Cl. 26o-428.5)

commercial success of lard oil manufacturing therefore depends to a large extent upon the yield of lard oil which commands awpreniium price over that of the raw material.

These same considerations apply to the treatment of vegetable and marine oils, a low pour point being the desideratum in refining edible oils and a high degree of unsaturation th desideratum in rening for many industrial uses. And in these cases too the oils are the premium products.

It is the purpose of this invention to provide an improved process for the separation of the more solid, high melting glycerides from the more liquid glycerides by which a greater yield of the liquid glycerides is obtained.

It is also the purpose of this invention` to provide a method for carrying out this separation which is rapid and continuous and is adaptable to large scale commercial operations.

The process of the present invention involves the processing of fatty oils in solvent solution and is conducted in the saine general type of apparatus utilized for the commercial solvent separation of fatty acids by the method disclosed in the patent to Latimer D. Myers and Victor J. Mucker heide, No. 2,293,676, issued August 18, 1942, for Method of Separating Fatty Acids."

The application of a solvent separation process to triglycerides was ilrst proposed by C. F. A. Simonin in United States Patent No. 144,000, issued October 28, 1873:

Tallow, lard, palm-oil, or any other animal or vegetable fatty or oily matter containing stearine, is rst dissolved in hydrocarbon, by preference such as is of a volatile character-petroleum or naphtha, for instance, or benzine or gasolinethe quantity of which, in respect to the fatty matter, should be such that the density of the solution will be from 35 to 45 Baum, according to the character of the said fatty matter. As the solution of the proper density becomes cool the stearine will crystalllze, and the oleine can be readily separated from it Iby filtration. decantation, or slight pressure.

Despite the antiquity of the proposal ofthe solvent separation of mixed triglycerides, the method has never been applied successfully or commercially to the manufacture of lard oil or to the fractionating of mixed fatty triglycerides except, possibly, in instances too obscure to have.

j ed to causing solid Noneof these inventors disclosed either a commercially expedient process or a continuousproc- `ess of accomplishing the desired fractionation.

The prior inventors apparently endeavored to find a special selective solvent, laboring under the misconception that a successful process depended upon nnding a solvent particularly adaptglycerides to precipitate while retaining the liquid glycerides in solution.

I have found that the principal requirement of a continuous commercial process is to obtain a precipitate of the solid glycerides which can be handled and filtered and which separates cleanly from the mother liquor containing the liquid glycerides. I have found that there are several factors which must be controlled in order to insure the formation of a filterable precipitate. f these the most important is the selection of the solvent. I have found that the lcharacter of the precipitate obtained from what I term a. semi-polar solvent is entirely different from that obtained from a non-polar solvent. By a semipolar solvent I mean one which contains -suiilcient oxygen atoms in the molecule to have an attraction for water as indicated by a limited but definite solubility of water in the solvent and of the solvent in water. I find have a solubility in water of from 1-25% and for water from l to 15% by weight at 20 C. Typical solvents of this type include isopropyl acetate, methyl ethyl ketone, ethyl ether, ethyl acetate, and methyl isobutyl ketone. The solubility of these solvents in water and the solubility of water in the solvents are not important characteristics per se, as related to the type of precipitate obtained, but merely characterize the solvents which I nd giveprecipitates consisting of discrete particles rather than amorphous slimy precipitates.

The solubility of water in the solvents is of importance in commercial operations in that most commercial fats at one time or another are contaminated with suspended water which becomes commingled with the fat and solvent during processing. The solubility characteristics of the solvents I propose for conducting a solvent separation are such that if an excess of water should happen to be present, the water will be precipitated from the fat solvent solution rather than the water dissolving and the fat being thrown out of solution.

The solvents which I have found suitable for the separation of triglycerides are generally of the chemical classes of ketones, esters, ethers, aliphatic nitro compounds or compounds containing one or more of these groups. They are capable of dissolving small amounts of water and still dissolving fatty oils. As a matter of convenience we prefer to use solvents. the boiling points of which are not too low, in order to avoid excessive solvent losses. High boiling solvents -although yielding a satisfactory separation present recovery problems and are therefore undesirable, particularly in processing edible oils where odor and flavor may be adversely aifected.

The preferred solvents Isopropyl acetate and methyl ethyl ketone satisfy the requirements exceptionally well.

By employing a solvent of the type specified filtration is very rapid and continuous vacuum or centrifugal filters may be employed for removing the precipitated solid glycerides. For example in processing cottonseed oilvin 33% solution I 4have found that filtration was complete in one minute when using isopropyl acetate as a solvent whereas 1% hours were required to filter an equal volume of a petroleum `solvent solution. The fast free filtering -precipitate results in cleaner separations and makes continuous operation practical. f

The second factor which I have found necessary to control is the concentration of the'fat in the solvent. I have found that the fat concentration should generally not exceed 50% by weight. The maximum concentration 'employable is dictated to a certain degree by the solid glyceride content of the fat being processed; the concentration of fat should not be so great that the volume of precipitate produces a thick pasty slurry which is diilicult to pump and process.

A second consideration which limits concentra-4 tion is the necessity of maintaining the polar nature of the solvent; if too great a concentration of fat in solvent is employed the solvent tends to lose its polar characteristics; in other words, the solid triglycerides are then being precipitated from a solvent which consists of polar solvent containing a large proportion of dissolved liquid triglycerides; such a mixed solvent is obviously much less polar in nature than the solvent itself.

I have found, taking these conditions into consideration that a concentration such that the fatty oil constitutes about 30% of the total solution is the most desirable concentration, for the fats and oils most commonly processed.

'Ihe third factor which I have found to be essential to operating a continuous commercial process is the method of chilling the solvent solution ofthe neutral fat. I have found that the precipitated particles of solid triglyceride are more fragile than has ordinarily been suspected and that it is therefore desirable to cool the solution with the minimum amount of mechanical working which tends to crush and destroy the precipitated particles. I have found that damage to the crystals can be greatly reduced by cooling the solution as rapidly as possible, thus reducing the time that the precipitate is subjected to mechanical treatment. I find that solid glycerides can be precipitated from the semipolar type solvents which I propose using, by very rapid chilling. The precipitates produced nlter very rapidly. This is in contradistinction to accepted methods of obtaining easily filterable precipitates which usually require very slow cooling to obtain a. desirable crystal or particle size. The cooling of solutions continuously on a large scale requires some sort of agitation of the solution in order to maintain cooling rates. With the formation of a precipitate of the type obtained by precipitating triglycerides which` tends to coat on and cling to the cooling surfaces, the agitator must necessarily be of the type whichI scrapes the cooling surfaces. I have found that the scraping of the cooling surfaces constitutes a most serious source of mechanicaldamage and that the rate of scraping should be kept to a minimum even though such a procedure is not in keeping with the best engineering practice which dictates the maintenance of heating and cooling surfaces at the highest possible degree of efficiency.

There are then two conditions to be met in retaining the best filtering characteristics of the precipitate. It so happens that vslow scraping of the cooling surfaces tends to reduce the fate of cooling which I have found is also important in order to reduce\the total time of agitation. It is therefore necessary to effect some compromise between these factors and then obtain speed of cooling by maintaining a high temperature difanimos ferential between the. cooling liquid and the solution being cooled.

i I havev found that it is desirable to cool the solution at a rate not less than .75 C. per minute with an oven-all chilling time after precipitation starts not to exceed 30 minutes. The rate at which the cooling surfaces are scraped should not exceed once every 3 to Gseconds.

By the use of the proper solvent, and concentrations and by obesrving the chilling precautions required, I have succeeded in processing fatty oils by a quick continuous process and btain for example in the case of white grease a yield of 'I0-80% of lard oil oi 40 F. pour point in 1/2 to 3A of an hour total processing time as compared to the 50-65% yields obtained by the conventional processes'requiring the better part of a week to complete.

The drawing discloses a diagrammatic representation of equipment suitable for the carrying out of my process. To container I for the fat and container 2 for the solvent are connected pipes 3 and 4 respectively, meeting at a point designated 5. In pipe lines 3 and 4 are disposed metering pumps 6 and 'I respectively. From point 5 pipe line 8 carries the solvent solution to a counter-current type of chiller 3 which comprises a series of conduits I0 through which brine or other coolant is circulated around chilling tubes I`I. Rotary Scrapers I2 are disposed in the chill ing tubes II. Any means desired may be utilized for rotating Scrapers. From the chiller, pipe I3 leads to the continuous rotary vacuum illter I4. The precipitate from the filter is melted and discharged through pipe I5 to a continuous still I6 and the ltered liquid is discharged through pipes II to a continuos still I8. Steam coils I9 and 20 are disposed in these stills respectively for distilling the solvent from the triglycerides. Both stills are connected to a condenser 2| (the details of which are not shown) for condensing the solvent to a liquid which is then returned through pipe line 22 by means of pump 23 to the solvent container 2.

This type of equipment is most economically built and operated if its size adapts it to handle approximately two to four thousand pounds of white grease per hour. A typical industrial unit handles thirty-six tons of white grease a day. This scale of operation produces between ten and eleven tons a day of ltered stearine and 26 tons a day of lard oil.

In practice substantially 3,000 pounds of white grease and 7,000 pounds of isopropyl acetate per hour are pumped from container I and 2 respectively to the chiller 9. The solution is then chilled from a temperature of substantially 32 C. to substantially minus C. after which it is discharged to the lter. For a separation of this type the filtering surface may be substantially twenty square feet and the rate of rotation onethird revolution per minute. This provides a iilter cake of optimum thickness. From the illl ter are recovered substantially 900 pounds of precipitate and 2,100 pounds of lard oil per hour, the precipitate having about a 35 C. melting point and the lard oil having about a 35F. pour point.

The conditions of the process may, of course, be varied somewhat to provide slightly different results. For instance, if it is not necessary to have a lard oil of quite so low a pour point, then the temperature need not be reduced as much. If a sharper fractionation is desired, then the concentration of white grease in solvent may be reduced. The lower the concentration oi the glyceride in the solvent, the more selective seems to be the action. Alsothe yield 4oi? lard oil increases as the concentration of grease in solvent isl dropped and decreases as the concentration goes up.

While the manufacture of lard oilv has been presented as the example of the utilization of my invention, still the method and apparatus may be used for processing other animal, vegetable, and marine fats and oils to alter theirA melting points and degree of unsaturation. 'I'hus sardine oil can be treated in substantially-30% concentration in solvent chilled to minus 30 C. to re`- move substantially 30% of the more saturated components. A lsh oil of improved drying properties results.

A series of examples indicating various possible conditions for carrying out the process are as follows:

Example No. 1

One hundred parts of commercial white grease were dissolved in 233 parts of disopropyl acetate. This solution was chilled to 3 C. at which point precipitation of the solids commenced. Chilling was continued at a rate so that the temperature decreased from 3 C. to minus 10 C. in 4 minutes. The solution was then filtered. The filtration rate was very rapid. The solvent was distilled from the solid and liquid portions. A yield of 72% of lard oil having a 35.2 F. pour point was obtained. The stearine obtained had a melting point of 33.8 C.

Example No.2

One hundred parts of commercial prime tallow were dissolved in 233 parts of isopropyl acetate. This solution was chilled to 14 C. at which point precipitation of the solids occurred. Chilling was continued at a rate such that temperature decreased from +14 C. to 5 C. in 5 minutes. The solution was then filtered. Filtration was exceptionally fast. The solvent was distilled from the solid and liquid portions so obtained. A yield of 55.2% of tallow oil having a pour point of 49.6 F. was obtained. The stearine obtained had a melting point of 50.6 C.

Example No. 3

One hundred grams of commercial white grease were dissolved in 233 grams of methyl isobutyl ketone. This solution was chilled to 1 C. at which point precipitation of the solids started. Chilling was continued at a rate such that the temperature decreased from 1 C. to minus 10 C. in 5 minutes. Filtration of this solution was practically instantaneous. The solvent was distilled from the solid and liquid portions. A yield of '76% of a lard oil, having a cold test of 31.6 F.. was obtained. The stearine obtained had a melting point of 35.4 C.

Example No. 4

Thirty parts of sardine oil were dissolved in 'l0 parts of ethyl acetate. This solution was chilled to 30 C. The solution was then ltered. Filtration of the precipitated solids took place readily. The solvent was distilled from the solid and liquid portions. A yield of 70% of liquid portion and 30% solid portion was obtained. The liquid portion showed considerably better drying properties than the original oil.

In summary, in the practice of this process a semi-polar solvent of the type indicated is pumped continuously by means of a metering pump and 7 l commingled with a stream of liquid oil or grease, which is also pumped continuously by a metering pump. The pumps are so adjusted that the con- 50%. This flowing stream of grease in solvent is then chilled at as rapid rate as possible, but with ing points, said method comprising continuously pumping liquid triglycerides into a flowing stream of solvent, the solvent characterized by a limited solubility in water of between 1 and 25 per cent by weight at 20 C. and by a limited solubility for water of between one and fifteen percent by weight at 20 C., the glycerides being added'at a rate effective to provide a solvent solution of thirty to fifty percent concentration by weight, then continuously passing the solution through a counter-current type of' chiller and continuously cooling the stream of solution at the rate of at 'least 035 C. per minute to form solidied glycerides on the walls of the chiller, removing the glycerides solidified at each local area of the chiller regularly at intervals of substantially every three to six seconds, then continuously conducting the slurry thus constituted through a filter and separating the solidied glyceride from the slurry, and evaporating the solvent for reuse.

2. A process of separating natural triglycerides into solid and liquid fractions which comprises dissolving the triglycerides in isopropyl acetate, chilling the resulting solution rapidly to effect a precipitation of the more solid triglycerides, re-

"mov'ing the solid triglycerides from the liquid triglycerides remaining in solution in the solvent, and then recovering the separated glycerides from the solvent.

3. A process of separating natural triglycerides into solid and liquid fractions which comprises dissolving the triglycerides in isopropyl acetate to form a. solvent solution of triglycerides in solvent oi' 30% to 50% concentration by weight, chilling the resulting solution rapidly at a rate of not less than 0.75" C. per minute in a continuous crystallizer, the cooling surfaces of which are scraped `regularly at intervals of from approximately 'three to six seconds, to effect a precipitation of the more solid triglycerides, removing the solid triglycerides from the liquid triglycerides remain- 60 centration of fat in solvent is substantially 30 to ing in solution in the solvent, and then filtering the separated triglycerides from the solvent.

4. A continuous method of separating mixed triglycerides containing saturated and unsaturated components into fractions of different melting points, said method comprising continuously pumping liquid triglycerides into a flowing stream of solvent, the solvent being of the class consist ing of isopropyl acetate, ethyl acetate and methyl isobutyl ketone, the glycerides being added at a rate eiiective to provide a solvent solution' of thirty to fifty percent concentration by weight, then continuously passing the solution through a countercurrent type ot chiller and continuously cooling the stream of solution at the rate 0f at least 0.75 C. per minute to form solidifiedglycerides on the walls of the chiller, removing the glycerides solidiiled at each local area of the chiller regularly at intervals of substantially every three to six seconds, then continuously conducting the slurry thus constituted through a lter and separating the solidified triglycerides .i

`1Rl!lralaltrsrclss CITED The following references are of record in the 'sie of this parent:

UNITED STATES PATENTS Number Name Date 1,974,542 Parkhurst Sept. 25, 1934 2,113,960 Grote Apr. 12, 1938 2,285,795 Batchelder June 9, 1942 2,298,501 Meyers Oct. 13, 1942 2,340,104 Brown Jan. 25, 1944 2,345,576 Buxton Apr. 4, 1944 2,352,883 Bolley July 4, 1944 OTHER REFERENCES Ind. and Eng. Chemistry, by Ferris et al., July 1931, pp. 753-761.

Oil and Soap, Bailey et al., 132.

Bull et al., Oil and Soap, July 1943. pp. 137-141.

Gregory, Uses and Applications of Chemicals and Related Compounds, p. 330, Reinhold Pub. Corp., N. Y. C., 1939. 1

July 1943. PP. 129- 

1. A CONTINUOUS METHOD OF SEPARATING MIXED TRIGLYCERIDES CONTAINING SATURATED AND UNSATURATED COMPONENTS INTO FRACTIONS OF DIFFERENT MELTING POINTS, SAID METHOD COMPRISING CONTINUOUSLY PUMPING LIQUID TRIGLYCERIDES INTO A FLOWING STREAM OF SOLVENT, THE SOLVENT CHARACTERIZED BY A LIMITED SOLUBILITY IN WATER OF BETWEEN 1 AND 25 PER CENT BY WEIGHT AT 20*C. AND BY A LIMITED SOLUBILITY FOR WATER OF BETWEEN ONE AND FIFTEEN PERCENT BY WEIGHT AT 20*C., THE GLYCERIDES BEING ADDED AT A RATE EFFECTIVE TO PROVIDE A SOLVENT SOLUTION OF THIRTY TO FIFTY PERCENT CONCENTRATION BY WEIGHT, THEN CONTINUOUSLY PASSING THE SOLUTION THROUGH A COUNTER-CURRENT TYPE OF CHILLER AND CONTINUOUSLY COOLING THE STREAM OF SOLUTION AT THE RATE OF AT LEAST 0.75*C. PER MINUTE TO FORM SOLIDIFIED GLYCERIDES ON THE WALLS OF THE CHILLER, REMOVING THE GLYCERIDES SOLIDIFIED AT EACH LOCAL AREA OF THE CHILLER REGULARLY AT INTERVALS OF SUBSTANTIALLY EVERY THREE TO SIX SECONDS, THEN CONTINUOUSLY CONDUCTING THE SLURRY THUS CONSTITUTED THROUGH A FILTER AND SEPARATING THE SOLIDIFIED GLYCERIDE FROM THE SLURRY, AND EVAPORATING THE SOLVENT FOR REUSE.
 5. A PROCESS OF SEPARATING NATURAL TRIGLYCERIDES INTO SOLID AND LIQUID FRACTIONS WHICH COMPRISES DISSOLVING THE TRIGLYCERIDES IN A SOLVENT OF THE CLASS CONSISTING OF ISOPROPYL ACETATE, ETHYL ACETATE AND METHYL ISOBUTYL KETONE, CHILLING THE RESULTING SOLUTION RAPIDLY TO EFFECT A PRECIPITATION OF THE MORE SOLID TRIGLYCERIDES, REMOVING THE SOLID TRIGLYCERIDES FROM THE LIQUID TRIGLYCERIDES REMAINING IN SOLUTION IN THE SOLVENT, AND THEN RECOVERING THE SEPARATED GLYCERIDES FROM THE SOLVENT. 